Hi Pat,
So as not to confuse newbies, you may consider changing or updating the Osama Bin Laden example in
http://www.ihmc.us/users/phayes/IKL/GUIDE/GUIDE.html#ContextsModalities
As they used to say on Star Trek, "He's dead Jim" (:-)
HTH, -- Adrian
-- Adrian
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Adrian Walker
Reengineering
On Mon, Jul 23, 2012 at 11:44 PM, Pat Hayes <phayes@xxxxxxx> wrote:
On Jul 23, 2012, at 8:16 PM, John F Sowa wrote:
> On 7/23/2012 6:22 PM, Pat Hayes wrote:
>> IKL is CL with the addition of a construct (that <sentence>) which allows
>> the formalism to refer to propositions. GIven that, you can then introduce
>> an *ontology* of things someone might want to call 'contexts' and say that
>> propositions (not sentences) are true or false in them. That was largely
>> the point of inventing IKL in the first place, in fact. But still IKL
>> is not a context *logic*.
>
> I agree with that point.
>
> PH
>> All I said was that CL and IKL are not context logics. You can axiomatize
>> a theory of contexts in them, as you please. I recommend IKL as it has
>> the expressiveness to encode content from just about any context logic
>> (and in many cases, to do a better job, IMO.)
>
> The last time I spoke with John McCarthy was in 2006, during the time of
> the IKRIS project. We had a short, informal meeting at Stanford about
> contexts and the IKRIS project. It included John, his student Selene
> Makarios (who was working on a theory of contexts), and Mike Genesereth.
And me. And it was then that I asked John about his basic logical construct 'ist', written as
ist(c, p)
and read as meaning " p is true in the context c". The question was, is the 'p' in this formula a sentence or a proposition? It is *written* in the McCarthy/Guha/Makarios context logics as a sentence; but to my delight, John said it was a proposition. Which is exactly what it is in the IKL way of writing this as a logical relation between two things, a context and a proposition:
(ist c (that p))
>From which I conclude that the IKL way of writing contextual truths is in fact closer to McCarthy's basic ideas than the context logic he developed to formally express them.
BTW, JMcC also had a clear answer to the question, what is a context, exactly? Which was, anything that you can write in the first agument position of an atomic ist sentence. That is, anything can be considered to be a context.
> John had been working on a context theory since the 1980s, and he had
> several students who developed versions. Guha was one of the first,
> with his PhD dissertation in 1991, which was also published as a Cyc
> technical report.
>
> At the end of the meeting, John explicitly said that it would be
> premature to standardize on any theory of context that had been
> proposed up to that point.
>
> I agree with him. But I believe that something like the 'that'
> operator is a prerequisite.
The key point about the 'that' operator is, that it obviates the need to make any fundamental change to the underlying logic. The basic logic of IKL is simply first-order reasoning of the very same kind that has been used since Peirce and Russell. Contrary to what JMcC and his students have claimed, one does not need a context logic in order to logically formalize contexts.
> There are many different ways of
> axiomatizing how you would use the 'that' operator to support
> a theory of context.
Yes, exactly. For a lot more on this topic, see
http://www.ihmc.us/users/phayes/IKL/GUIDE/GUIDE.html#ContextsModalities
Pat
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